1. Field of the Invention
The present invention relates to signal transmission using a eigen antenna technique, and more particularly, to a signal transmission apparatus using a eigen antenna technique capable of improving quality of a down link signal using residual antennae in a wireless communication system using more antennae than the number of transmission signals and a method thereof.
2. Description of the Related Art
When a signal is transmitted using a plurality of antennae in a wireless communication system, a capacity of a system may be increased. In particular, a Bell Lab. Layered Space-Time (BLAST) scheme capable of acquiring a multiplexing gain, a Space-Time Block Coding (STBC) capable of acquiring a diversity gain, and a beam-forming scheme capable of acquiring power of a received signal may be included in a representative time-space signal processing scheme using a multiple antenna.
In an existing wireless communication system, a transmitter needs M antennae to transmit M transmission signals when there are M time-space signal processed signals. However, when there are N (>M) antennae, M antennae are fixedly selected and used from the N antennas. For example, there are four antennas for a base station in a case of a Wireless Broadband (WiBro) system. However, only one or two antennas may be used to transmit a signal during a down link interval. When there are transmission antennae more than the number of required transmitted signals, an adaptive use of residual antennae may improve quality of a received signal. Channel information for adaptively using the residual antennas may be estimated by a receiver and transmitted to a transmitter.
However, since the method of the related art needs an additional feedback channel, it should correct communication protocols. A receiver has a burden to transmit N-M separate pilot signals to estimate channel information for the residual antennae. This also causes correction of the communication protocols.